No, in order to save all of us from apps that kill our batteries, Apple does not allow apps to continue to run in the background for more than a few minutes. There are only very special limitations (music playing apps, VOIP, navigation apps, etc.) which permit ongoing operation. In terms of details, this is described in About the Background Execution Sequence.
If you want to notify user of something at some future time, you can use local notifications. When you do this, though, you don't control whether your app restarts or not. Only if the user taps on the notification (assuming they even granted your app notification privileges at all), will the app be reopened. For more information, refer the the local notification discussions in UserNotification framework documentation. But note, this is not intended for alerts every 45 seconds, but rather for a significant notification scheduled for some future time.
For discussion of how one might marry local notifications with timers, see swift NSTimer in Background and this follow up question swift calculate time for timers running in background.
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